Monthly Archives: January 2016

EPS on wall

Working with Expanded Polystyrene (EPS) Insulation

EPS insulation is a fantastic product designed to insulate external buildings, whilst at the same time providing a robust and long term solution. The EPS for external wall applications is retailed is packs of varying thicknesses and can be cut and shaped to size depending on the requirements of the customer. Hopefully after going through this blog, you will see how easy it is to actually work with the expanded polystyrene (EPS) on external wall applications.

How is the EPS supplied to the installer?

Depending on your requirements the EPS can be cut to any level of thickness (20mm to 200mm+), but the standard external wall insulation products are packaged with the following thicknesses of the boards:

  • 20mm
  • 50mm
  • 70mm
  • 90mm
  • 100mm

If you are insulating a solid wall property and you would like it to meet the current building regulations for energy efficiency (a u-value of 0.3 or better), then using a thickness of 90mm+ is what you will be after.

20mm and 50mm insulation boards are normally used to already supplement an already insulated wall (usually a cavity wall) where the space is at a premium.

20mm insulation is also thin enough to use on the window reveals and where you want to provide a nice even substrate to apply the layer of render. Note: the 20mm EPS is too thin to drill in the mechanical fixings.

How is the EPS handled during the installation process?

The good news is that EPS is very easy to cut – you can simply use a saw or a hot knife. When using a saw you will have to be really careful because the cutting process will cause debris to scatter around the site. We recommend doing it in a sheltered area or under the netting that is placed around the scaffolding.

If you would really like to have the best piece of kit for this process, then we recommend using the hot wire cutter. As mentioned above, using a saw or knife can lead to a jagged edge or messy finish, with bits of polystyrene flying around the install area, the wire cutter slices through the EPS like a hot knife through butter, leaving minimal waste and providing a precise accurate finish!

The EPS boards themselves need to be installed in a staggered formation, as illustrated in the EWI Pro Installation Manual. Additional diligence needs to be applied when going around openings and corners – please refer to the relevant installation diagrams.

When the mechanical fixings are installed, ensure you minimise the thermal bridging between the anchors and the EPS material itself. Best way to do this to insert the EPS caps on top of the fixings – fixing them into position using the foam adhesive OR simply use the EcoDrive fixings, which don’t have such limitations.

Rasping the EPS to provide a nice and even substrate

The surface of the grey (platinum) EPS can get pretty oily and needs to be rasped before the basecoat is applied on top. You can use a flat trowel or the angled for different applications. The angled one works very well for corners and the flat trowel is perfect for all other EPS surfaces.

Rasping can be quite a messy process with the EPS bits potentially flying around to all parts. Best to have netting around the scaffolding or the area you are working on – ideally you will have an industrial vacuum, so as you rasp the debris are sucked up and cleaned before it becomes an issue.

Storing your EPS safely

Although the EPS is fairly robust, it works best when it is not exposed to the external elements for a period of time. To ensure the EPS remains a robust product it needs to be stored away from direct sunlight and shielded from rain and wind.

The best bet is to work with the EPS behind a layer of netting – this will keep away direct sunlight. When you are not working on site, ensure that you store the EPS in a dry place away from the elements. Try to use protective sheeting and potentially store in a shed or garage to avoid extermities in temperature.

baner renders_wersja2

Acrylic Render vs. Mineral Render vs. Silicone Silicate Render

Here at EWI Store, we source our renders from EWI Pro who offer a broad range of BBA Approved renders. Whether it’s a classic Silicone Render or a traditional Monocouche render you’re after, we can cater to all requirements!

Nevertheless, the most popular renders within the EWI Pro catalogue are the Mineral Render, Acrylic Render, Silicone Silicate Render. As you might expect we get asked a lot what the difference is between these types of render and which is the best? Well, in this blog we thought we would try and explain the differences so you can pick the right render for your next job! If you’re looking at getting an idea of how much coloured render costs per m2, then check out our blog post which gives a really comprehensive idea of all the components.

Mineral Render

Our EWI Pro Mineral render is the only one to come as a dry mix – you need to add water to it before applying it. It also requires painting afterwards, which means it is a bit more time intensive to install. So why do people use it? Well there are a few reasons – firstly it is cheap in terms of material costs. Secondly mineral render dries much quicker than all the other types of render we offer so if you are installing in wet climates (I know most of the UK is normally under the water!) the this is the stuff to use – by the same token, this quick drying render is the one to use if you are installing in particularly humid or cold conditions since it will help minimise wash-off (when the render doesn’t stay in place due to rain or other unforeseen weather conditions!).

In terms of installs around the country, Mineral Render is particularly popular in both Wales and Scotland due to temperature and volume of rain. If you are doing the install yourself and it is during the summer months, the other renders just require the one coat (the colour is within the render itself) so you won’t have to paint anything once the render has been applied. Mineral render is also breathable and therefore compliments our Rockwool (Mineral Wool) insulation very well.

Once the Mineral Render has been applied it needs to be painted with our EWI pro Silicone paint which will provide a long lasting barrier to the elements and obviously can be coloured to your requirements.

Acrylic Render

What is Acrylic Render? Well for years has been the installers render of choice – it is essentially a render containing acrylic resin. Acrylic Resin is a type of plastic and added to render it helps offer better stain and water resistance as well as greater resistance to cracking. Our acrylic render comes pre mixed; this means that it can be applied straight on to the substrate (e.g. wall) without mixing it first with water. We sell the EWI Pro acrylic render pre mixed with your colour of choice and what is really great about it is when you opt for a vibrant colour, the acrylic render will hold this colour for a long time without fading (the other renders and the Silicone Paint will fade over time so may require painting every 10 years or so).

Acrylic Render is the most cost effective render when you consider the labour and material costs – requiring just one application. If you are looking for the best value system then this in our opinion is the best and certainly a huge improvement on the old sand and cement renders of the past – it is flexible and will last 20 years plus. Before you use the acrylic render though just a couple of things to consider – firstly it is not breathable. The Acrylic Resin / plastic in this render means that nothing is going to get through it, therefore it is definitely not worth putting it on a breathable insulation product like our Rockwool or Wood Fibre as it sort of defeats the point! In addition, EWI Pro Acrylic render is not worth installing when the weather isn’t very good, so cold or wet as it takes longer to dry than the Mineral Render system. Finally Acrylic render is not as resistant to the elements as our Silicone Silicate render, so there will be some maintenance required like cleaning over time.

Silicone Silicate Render

This is now our installer’s render of choice – the EWI Pro Silicone Silicate render is ready mixed (much like our Acrylic Render) and therefore can be applied straight to the substrate. It is comprised of Silicone resin and Silicate. Once installed on the wall the Silicone Silicate render is hydrophobic, which basically means it repels water and therefore can be considered self cleaning in that the water will simply run off it.

The Silicone Silicate render comes in a few various different textures, but by far our most popular is the 1.5mm render (read our full guide to render grain sizes). This means that within the render, it has Silicate granules just 1.5mm in diameter, so it can be applied extremely thinly on the wall – the advantage of this is that it is extremely flexible, so the house moves and the render moves with it. It simply won’t crack!!

Again, much like the Acrylic render we don’t advise installing this render during the harsh winter months or when it is raining as the system does take a few days to cure – but once installed it should be maintenance free for over 20 years although it make require the odd pressure spray from time to time to keep it nice and clean. The EWI Pro Silicone Silicate render is completely breathable so is the ideal partner for our mineral wool insulation products.

If you would like to get a quote for any of these materials try our new materials calculator by clicking on the picture below

All the renders we sell in the EWI Pro Insulation System range are BBA Approved –  Products that receive Agrément Certificates are recognised by building control, government departments, architects, specifiers and industry insurers. It’s a mark of quality, safety and reliability that provides reassurance that the product’s fit-for-purpose.

To learn more about the BBA and the EWI Pro Insulation System products please click here.

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Materials used in the EWI Pro EPS external wall insulation system

The EWI Pro EPS external wall insulation system is made up of several components – including everything from the preparation materials, the insulation (itself), the basecoats and top coats. It is absolutely paramount to use the right components in the installation process to ensure the integrity of the system and to uphold all the necessary system designer product warranties.

Using the wrong EWI Pro components may not appear to be a problem initially, but can lead to problems further down the line. We recommend you follow the step-by-step installation guides to achieve the optimal end solution.

The EWI Pro EPS external wall insulation system is a BBA approved system and specifies the name and number of each component to use. The BBA document goes into quite a lot of detail, including how to apply the adhesive to the insulation, setting out the number of fixings per EPS board and how much basecoat to add before the mesh is sunk.

The following section introduces each component of the system and goes into a bit more detail on how it is applied in the live job.

Priming the walls with EWI Pro Substrate Primers

We always recommend priming the walls before undertaking any render or EWI installation. At EWI Store, we offer a range of substrate primers which are suitable for a variety of surfaces; for example our Water Based Primer or our Universal Primer. 

Although the priming of the walls is outside the scope of the BBA, it is highly recommended to undertake before any insulation is actually applied. Priming the walls ensures that the walls are prepared for the insulation and the adhesive.

Biocide products, such as our Fungicidal Wash, can also be applied before the actual primer – this serves to remove any biological growth on the walls and prevents their build up. This is great to do if your walls have had previous attacks from biological agents.

Priming is also good to do to cover over any hairline cracks and bind any loose surface debris to the substrate. A nice and firm surface is a fantastic starting point for the insulation, which will make the adhesion stage a ‘walk in the park’.

Sticking the EPS using the EWI Pro adhesive

When applying the EPS boards to the wall you can use the EWI-210 EPS Adhesive or the EWI-220 Basecoat. You will need to follow the EWI Pro installation standard when dabbing the adhesive on the back of the board. The adhesive needs to go all round the perimeter of the board and have at least 2 or 3 dots dabbed in the middle of the board.

Both the EWI-210 and EWI-220 need to be mixed with water and prepared before the works start. The packs of adhesive and basecoat come in 25kg bags and each one will cover about 3m2. When mixing the adhesive make sure you use a low speed mixer to start off the process. Once mixed set it aside for at least 10mins to allow the fibres in the material to bond – then you should be ready for the installation process.

Installing the Mechanical Fixings

Eco Drive EWI FixingThe mechanical fixings or anchors are produced by specialist companies for the use in external wall insulation system design. Traditionally plastic fixings were quite popular as anchors but over time ones with metal rods have also been used. The metal and plastic fixings require quite a bit of preparation works and can add quite a bit to the installation time. For example, to avoid the cold bridging each of the ends of the plastic head should be capped off with a rounded piece of EPS plug – stuck together with foam adhesive.

Due to this extra work with the traditional fixings, this is the reason that we fully endorse the EcoDrive (self-drive) fixings. With the EcoDrive fixings you still have to prepare the holes in the walls for the wall plugs, but you can then use a mechanical screw-drill to self-drive the fixings into the insulation and the walls.

According to EWI Pro you should use 5.5 fixings per m2 of EPS board. This together with the adhesion stage in the previous process will provide a nice and robust insulation layer.

Sinking the Fibreglass Mesh into the Basecoat

Installing the FibreEWI-220 EPS Basecoat - 25kgglass Mesh into a layer of basecoat binds the insulation layer together and prepares a nice substrate ready for the top coat.

With the EWI Pro system we recommend using the EWI-220 EPS Basecoat. Please do not use the EWI-210 Adhesive as this will not work optimally and will void you the manufacturer’s warranty. Just like the adhesion layer the basecoat is prepared the same way – adding the bag of powder to the set amount of water.

For this stage, using a notched trowel, the Fibreglass Mesh is sunk into the layer of basecoat. For more details, please refer to the EWI Pro Installation Manual for EPS.

The EWI-220 EPS Basecoat is designed to dry quickly but you should leave this coat to set for at least 48-72hrs. If you have been using the EWI Pro products for a while, then use your best judgement. Sometimes you need to make a call based on the atmospheric and site conditions and add more/less time to this process.

Prime using the SiSi or the Mineral / Acrylic primers

As mentioned in the previous section the type of primer you use is determined by the top coat. For example, for silicone silicate render we recommend using the EWI-333 SISI Silicone Silicate Primer; for Mineral Mender we recommend using the EWI-330 Mineral & Acrylic Primer.

The primer can be applied mechanically with a roller or a brush. If you use a spraying machine, then you can use this too.

Leave the primer layer to dry for at least 24hrs before applying the top coat.

Applying the top coat render

You can apply different types of finishes – such as render, scratched render, dash or brick slips. But to keep things nice and simple we recommend the grained render every time.

The EWI Pro render comes in different grain sizes – available in 1.0mm, 1.5mm, 2.0mm and 3.0mm. The 1mm render is virtually smooth with the 3.0mm render being quite rough. Bigger grained renders are actually applied with a thicker coat – the thickness of the coat render should be synonymous with the grain size. So when applying 2.0mm render the thickness of the coat should be no more than 2.0mm thick.

Most installers quite like installing the 1.5mm grained render as it is sits nicely in the middle of the other grain thicknesses and aesthetically it looks really great.


Different types of EWI Pro renders available:

The renders are sold in liquid form and come in 25kg buckets, apart from the Mineral Render, which is cement based and requires another layer of Silicone Paint to complete the installation. The liquid based renders can be applied straight onto the walls and can be coloured with different pigments – so you can achieve any colour of wall that you like.

Mineral render requires painting!

When you have applied the EWI-060 Mineral Render on the wall, you will need to wait for it to set before painting it. The render is mixed a bit like the adhesive and the basecoat – using a low speed mixer, adding the powder to a bucket of water.

When the render is dried, we recommend using the EWI-004 Silicone Paint, which in fact can be coloured to achieve any coloured finish the customer wants.





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Why to use EWI Pro for your next Rendering job

Applying a coat of render to the outside of a property is a fantastic way of giving it a facelift, especially if the existing exterior is in poor condition.

The days of simple sand and cement render are numbered however, since they unfortunately simply don’t stand the test of time. While it looks nice when this type of render is initially applied, very quickly cracks will appear.

The reason is that it has no flexibility

Over the course of the year a property faces a huge variation in temperature – at the peak of summer the external air temperature might be in excess of 30 degrees while during the cold winter months the temperature might drop to below zero. While the house and the mortar (full of lime) can adapt to these changes in temperature, the sand and cement render can’t. What happens is that it will start to crack – leading to a pretty big issue – damp!

A huge amount of water hits a wall during a year and this will travel down to these hairline cracks. The water then gets pulled in through capillary action sometimes right through to the internal wall where damp patches appear. Even so, water travelling behind the render and the external wall will very quickly cause complete failure of the render system.

So you have a property and want to get a new coat of render – what do you do?

Use EWI Pro flexible renders for the best render finish

Our EWI Pro silicone silicate render, mineral render and acrylic renders are all specifically designed to combat this cracking issue – they are flexible (as well as being aesthetically pleasing and hydrophobic) so will move with the building – so no cracks!

Available in thousands of colours, our collection of renders are the perfect solution for modern rendering providing an extremely long last protective layer to the external walls of a property ensuring it really does stand the test of time. Couple this with the flexible underlying reinforcement layer (EWI-220 Adhesive + EWI640 Reinforcement Mesh) and you have the perfect system that is easy to work with and gives unbeatable performance.

Fresh render vs tired render

All the EWI Pro renders we offer have gone through the BBA accreditation – this is the most recognised building certification scheme in Europe illustrating the extremely high quality of the EWI Pro renders.

At EWI Store we are extremely proud to be able offer EWI Pro at unbeatable prices, so before you complete your next rendering jobs please do consider the EWI pro system. We also offer training in conjunction with EWI Pro at fantastic rates for those looking to familiarise themselves with the EWI Pro family of products as well as more advances courses for those looking to take things a bit further.